Protected carbon electrode



Patented Mar. 24,1931

Eur OFFICE ROBERT SUCHY, KARL STAIB, AND WILHELM MOSCHEL, OFIBITTERFELCD, GERMANY,

ASSIGNORS T GQIEARIBENINDUSTRIE AKT'IENGESELLSCHAFT, OF FRANKFORT-ON-THE-MAIN, GERMANY, CORPORATION OF GERMANY PROTECTED CARBON ELECTRODENo Drawing. Application filed December 6, 1928, Serial No. 324,322, andin Germany December 28, 1927.

This invention relates to the method of protecting carbon-electrodesfrom oxidation.

Electrodes for use in electric furnaces, e. g. in cells forfusion-electrolysis, are generally subjected to considerable wear owingto the oxidizing action of the surrounding air on those parts of theelectrode which project from 'the interior of the furnace. A largenumber of means have already been proposed for obviating thisdetrimental efiect. All of them, however, according to our knowledge,have hitherto failed to produce a definitely favourable result.

We have now discovered that this object of protecting electrodes fromoxidation may be effected to a hitherto unattained degree by A soakingthe surface of the baked electrode with a concentrated solution of phoshoric acid. The effect will be shown clearly y the following instances:

(1) An ordinary graphited carbOn-elec trode, being kept at attemperatureof about 500 C. and allowing free access to the, air, was found toundergo considerable oxidation within 36 hours, whilst a similarelectrode, previously soaked with'phosphoric acid and then subjected tothe same conditions for ten days and more, displayed no sign of wear dueto oxidation.

(2) By soaking the upper part of an ordinary-carbon-electrode,projecting from a cell for fusion-electrolysis, with phosphoric acid,

the attack of the surface of the electrode by oxidation was completelyinhibited.

It is sufficient to subject to the treatment described only such partsof the electrode as are exposed to the air. The concentration of theacid used for the treatment appears to be of small account;

however it is preferable, for other reasons, to

In testimony whereof *we have hereunto set f apply a concentrated acidcontaining at least 50 percent of H PO 'The solution of phosphoric acidis preferbrush; Having new claim:

A carbon-electrode, containing phosphoric acid in the'parts of thesurface exposed to the atmosphere when used in an electric furnace.

. ably applied to the electrode by means of a described our invention,we

